Driving In Snow

[Nlitenme]

It's been awhile since I've signed in. But with winter coming soon I want to know how you like driving in the snow. We just got our first snow yesterday and when I turned on my 4 wheel drive button, it came on then the light went out. I looked at the owners manual and apparantly the 4-wheel drive is only supposed to be used and will stay on when driving on gravel or deep snow or needing traction when stuck. It does not stay on all the time like my Toyota 4-wheel drive truck did. Do any of you suggest I get studs or will all season radials be fine. I'm a little disappointed in this. It was a peace of mind to know 4-wheel drive was on even though I am very careful and drive according to conditions of the road.

Thanks.

[bothwell_buyer]

It's been awhile since I've signed in. But with winter coming soon I want to know how you like driving in the snow. We just got our first snow yesterday and when I turned on my 4 wheel drive button, it came on then the light went out. I looked at the owners manual and apparantly the 4-wheel drive is only supposed to be used and will stay on when driving on gravel or deep snow or needing traction when stuck. It does not stay on all the time like my Toyota 4-wheel drive truck did. Do any of you suggest I get studs or will all season radials be fine. I'm a little disappointed in this. It was a peace of mind to know 4-wheel drive was on even though I am very careful and drive according to conditions of the road.

Thanks.

depends on the quality and depth of snow - but if its bad then only good tyres with adequate tread will work - I doubt if my Fawlkens used for racing will be much good in the snow so the racing rav will be tucked away somewhere warm. The other RAV will be shoed up with deeper tread tyres....unless I get my landrover back which is equipped with tyres that would drag it up a glacier if only the engine could cope!

[Roadwrangler]

It's been awhile since I've signed in. But with winter coming soon I want to know how you like driving in the snow. We just got our first snow yesterday and when I turned on my 4 wheel drive button, it came on then the light went out. I looked at the owners manual and apparantly the 4-wheel drive is only supposed to be used and will stay on when driving on gravel or deep snow or needing traction when stuck. It does not stay on all the time like my Toyota 4-wheel drive truck did. Do any of you suggest I get studs or will all season radials be fine. I'm a little disappointed in this. It was a peace of mind to know 4-wheel drive was on even though I am very careful and drive according to conditions of the road.

Thanks.

Hi,

I'm fairly new to Rav's, and I don't know which model you have, but I'm pretty sure the button your pressing on the dash is actually a diff lock button, for extreem conditions, on tarmac you'd probably find with it pressed you wouldn't be able to steer the car and may well damage the transmition. I believe the earlier Rav's are all full time 4WD anyway, and the later ones with VSC run in 2WD and engage 4WD when the system detects its needed. I think some of the latest Rav's are only 2WD however.

As for tyres, an A/T (all terrain) or M+S (mud and snow) will always give better grip on the slippery stuff.. I had some A/T's called Nangkang 'Wide Conquerer' on my old Pajero, they lasted nearly 3 years using the car daily, never put a foot wrong in the snow and were actually very good in the wet or dry on tarmac, and were about half the price I was getting wuoted for Duellers at the time.

Regards Austin..

[local hero]

It's been awhile since I've signed in. But with winter coming soon I want to know how you like driving in the snow. We just got our first snow yesterday and when I turned on my 4 wheel drive button, it came on then the light went out. I looked at the owners manual and apparantly the 4-wheel drive is only supposed to be used and will stay on when driving on gravel or deep snow or needing traction when stuck. It does not stay on all the time like my Toyota 4-wheel drive truck did. Do any of you suggest I get studs or will all season radials be fine. I'm a little disappointed in this. It was a peace of mind to know 4-wheel drive was on even though I am very careful and drive according to conditions of the road.

Thanks.

HI + welcome, if you scroll down the page to a post entitled "what does a diff locck actually do" Anchs gives a full answer of how your 4x4 works on various models, Trust me it will switch to 4 wheel drive if + when its needed Stew

[webleymk3]

if you scroll down the page to a post entitled "what does a diff locck actually do" Anchs gives a full answer of how your 4x4 works on various models, Trust me it will switch to 4 wheel drive if + when its needed Stew

Local Hero.. you beat me to it! Was just about to say that!

Link to thread...

[anchorman]

Yes and just to add, unlike a Honda CRV and many of the others, your RAV spends a lot of time in 4WD even on a good road surface and will steplessly reduce the amount of drive automatically. The Honda and others with a "Haldex" unit, require one of the front wheels to slip before it can engage the 4WD automatically.

The 4WD lock button on a RAV 4.3 will engage the rear axle but to ease the load on the transmission it disengages it automatically at 25mph.

[Toha]

Yes and just to add, unlike a Honda CRV and many of the others, your RAV spends a lot of time in 4WD even on a good road surface and will steplessly reduce the amount of drive automatically. The Honda and others with a "Haldex" unit, require one of the front wheels to slip before it can engage the 4WD automatically.

The 4WD lock button on a RAV 4.3 will engage the rear axle but to ease the load on the transmission it disengages it automatically at 25mph.

Totally agree with you ... Forced four-wheel drive is automatically turned off at speed over 40 km/h ....

my opinion - to put the good winter tires, all the rest will make electronics

[*srjp*]

On this theme I'm becoming more concerned by the apparent inability to disable the stability and traction control on the 4.2 XT4. At times I've been forced to lock the front/rear diff on cars to get them out of snowed in car parks and mountain tracks. If the brake and door dance doesn't work as on the 4.3, can a fuse not just be pulled to kill them? Loss of ABS wouldn't be a problem either. It would be a last resort technique but come well before getting towed out by a Land Rover...

Edit: Handbook says...

Fuses (Type a)

12 ABS 2 30 A (Found in the engine compartment)

Anti lock brake system, vehicle stability control system, traction control system, brake assist system.

Seems to be the ticket. Is there any reason removing this fuse temporarily to release a vehicle from sand/snow/etc would cause damage to the ECU or other devices, or perhaps even prevent the car starting?

[anchorman]

I think that is one you would just have to try. The beauty of the 4.2 is that the underlying system is mechanical so in theory pulling the fuse should work. If it does you could then add a switch.

[shcm]

Yes, of course the best way is to try it.

Just to add though, what you have to consider is what else the VSC/ABS ECU is communicating with. In a modern system, it is not uncommon for the VSC/ABS ECU to be sharing some of its sensor information over a CAN bus with other ECUs. For example, wheel speed data is a favourite on some vehicles (although Toyota have a habit of using a separate wheel speed signal). Yaw rate data is another.

Looking at the documentation for the later 4.2s, the CAN comms looks fairly simple. The ABS/VSC ECU would appear to sit on a CAN bus, just talking to a steering angle sensor and a yaw rate sensor.

ABS2 fuse does appear to be the main permanent power supply for the ABS/VSC ECU. The ABS/VSC ECU's signal to "turn on" is via ECU IG fuse.

On the other hand, unless I've missed something, the steering angle sensor would appear to have a permanent Battery feed from the 10A dome fuse and an ignition switched "turn on" signal via the 10A ECU IG fuse.

The yaw rate sensor would appear just to be supplied with a switched Battery feed through the IG ECU fuse. I'm not sure what else is off that fuse.

Now, the next bit is pure guess work (well part of it is). As the yaw rate and steering angle sensors have CAN comms ability, they will have microcontrollers (processors) in them, which also means they have the capability to store DTCs.

Potentially, if you've disabled the ABS/VSC ECU but not the other two sensors, when you power up the vehicle, the two sensors may store DTCs due to the fact they are not receiving CAN comms from the ABS/VSC ECU. The diagnostic tester also connects to this CAN bus, so it is not unreasonable for the sensors to store faults. If, when the two sensors re-establish comms with ABS/VSC ECU (when the ABS2 fuse is replaced), the stored DTCs (or previous fault condition) may even be communicated to the ABS/VSC ECU, with the result that it turns the fault lamp on. That may be less likely though.

You could pull all the fuses mentioned, then the above can't happen, but I'm not sure what else is fed off the ECU IG fuse (for example) which may be essential for running the vehicle.

Chances are if you try it, none of the above may happen and any stored "faults" are not going to stop you getting the vehicle unstuck anyway. It would be interesting to know what really does happen, rather than me "theorising". Anybody can do that until they are blue in the face and it never proves anything :D

The 4.2 CAN network looks fairly simple really. Trying something similar with a 4.3, is a completely different saucepan of eels. All sorts of stuff is shared over CAN between lots of important ECUs and you could end up with a whole assortment of warnings on starting up.

[bonjo]

the 4WD on 4.2 is full time and 50/50 split in normal condition. Power is varied between the front & rear axle when traction is lost. This is done via a central diff (in RAV 4's case is called the trans-axle)which is viscous coupled: slippage changes the oil viscosity and varies the front/rear torque.

RAV 4.3 normally operated in FWD mode; when traction is lost, power is diverted to the rear axle. When you press the 4WD button is effectively acts as a central diff lock which send fixed power to both axles(I presume it is 50:50 as on most locks). Now this will cause what is known as diff wound up if you start going round corners and loads the diff in worse case the car comes just stops!

However you are only supposed to use this on slippery surface where the transmission wind up will get the tyres to slip (I know it sounds silly) in order to unload the transmission. This is why you should not use any form of diff lock on non slippery surface and I guess in the case of RAV, they have decided once you are above xx mph, the grip is good and the diff lock is automatically dis engaged to avoid potential damage to the transmission.

On the subject of ABS, on 4.2 this is automatically disengaged at speeds below 5~10 mph which is what you want in off road/ slippery situation. Don't confuse this with hill descent function some cars have

[anchorman]

Bonjo

There is no viscous coupling on a 4.2 and the 4.3 does not only transmit drive when the traction is lost, it does it variably and automatically for most of the time

[*srjp*]

Blimey, had to read schm's post twice there, and quite slowly each time...

Very interesting though, thanks.

Warning lights generally don't upset me too much, my last two cars have had the ABS one on for months at a time without any noticeable issues (had the pads and discs checked each time; all working fine), but I have been considering one of those OBD2 readers and that's another motivating factor for it.

I'm more than happy to let all this rest in theory-land for now, but should it come to it I'll definitely be back here to let you both know what occurred!

[shcm]

Blimey, had to read schm's post twice there, and quite slowly each time...

I'd better not read it back to myself, it probably doesn't make sense

.........but I have been considering one of those OBD2 readers and that's another motivating factor for it.

While any form of reader is no doubt a good investment anyway, just bear in mind that OBD/OBD2/EOBD applies to engine management only. Reading and clearing faults from the other systems is still in proprietary mode. So you'd need a reader that talks Toyota or use some of the other methods (mentioned elsewhere on here) that at least Toyota builds in.

[*srjp*]

Ah, I knew it started as a drivetrain thing but didn't realise the potential of many devices was still limited to that area. I'll have a proper read-up on the forum before purchasing one, thanks again for the heads up.

[Roadwrangler]

Potentially, if you've disabled the ABS/VSC ECU but not the other two sensors, when you power up the vehicle, the two sensors may store DTCs due to the fact they are not receiving CAN comms from the ABS/VSC ECU. The diagnostic tester also connects to this CAN bus, so it is not unreasonable for the sensors to store faults. If, when the two sensors re-establish comms with ABS/VSC ECU (when the ABS2 fuse is replaced), the stored DTCs (or previous fault condition) may even be communicated to the ABS/VSC ECU, with the result that it turns the fault lamp on. That may be less likely though.

You could pull all the fuses mentioned, then the above can't happen, but I'm not sure what else is fed off the ECU IG fuse (for example) which may be essential for running the vehicle.

Chances are if you try it, none of the above may happen and any stored "faults" are not going to stop you getting the vehicle unstuck anyway. It would be interesting to know what really does happen, rather than me "theorising". Anybody can do that until they are blue in the face and it never proves anything :D

The 4.2 CAN network looks fairly simple really. Trying something similar with a 4.3, is a completely different saucepan of eels. All sorts of stuff is shared over CAN between lots of important ECUs and you could end up with a whole assortment of warnings on starting up.

If you start pulling fuses or dissabling circuits, won't it just trigger the MIL light and poentially put the vehicle in Limp Home Mode (assuming it has one)

[bonjo]

Bonjo

There is no viscous coupling on a 4.2 and the 4.3 does not only transmit drive when the traction is lost, it does it variably and automatically for most of the time

I am only repeating what toyota technical people sent me when I asked them about the 4WD torque split system when I was in the process of buying my new 4.2. There are certainly no electronic gadgetry involved that I know of but then again I don't have detailed written technical info on 4.2 4WD system.

I was also told when thinking about changing to 4.3 that nearly all the drive goes to the front under normal condition. This kind of agreed with my thoughts after a test drive when 4.3 came out, I found the car too understeery; like FWD cars.

Drive split happens continuously as you mention but only when slip is detected which is how most of the new bread of small SUV's operate.

[downtime]

The Honda and others with a "Haldex" unit, require one of the front wheels to slip before it can engage the 4WD automatically.

I was under the impression that RAV4's system is also Haldex. 3rd Gen to be exact. The newer VW 4WD use the 4th gen Haldex. Audi Quattros use Torsen. The maximum axle distribution is 55/45 in Rav and 50/50 in 4th gen Haldex. Torsen has 40/10 all the time and maximum 50/50 when needed.

Rav also needs the front wheels to slip before it start to move power to the rear wheels. In take-offs there's always some power directed to the rear wheels no matter if it's slippery or not.

This is coming out for memory so those with better memory, please correct if I'm wrong.

[Davrav]

The Honda and others with a "Haldex" unit, require one of the front wheels to slip before it can engage the 4WD automatically.

I was under the impression that RAV4's system is also Haldex. 3rd Gen to be exact. The newer VW 4WD use the 4th gen Haldex. Audi Quattros use Torsen. The maximum axle distribution is 55/45 in Rav and 50/50 in 4th gen Haldex. Torsen has 40/10 all the time and maximum 50/50 when needed.

Rav also needs the front wheels to slip before it start to move power to the rear wheels. In take-offs there's always some power directed to the rear wheels no matter if it's slippery or not.

This is coming out for memory so those with better memory, please correct if I'm wrong.

The 4.3 RAV utilises an 'electromagnetic coupling' to achieve the drive distribution

[bonjo]

this is turning into an interesting topic! Been a while for me after I sold my Mitsubishi shogun!

As downtime mentioned, Audi quatro started off with Torsen; VW went with halfex for their 4 motion models. I could be wrong but think Japan favoured viscous coupling (as it is on the Shogun) until the cuurent range of supermarket SUV arrived where I think is electro mechanical such as 4.3, Honda's and Nissan's but not the Freelander. I think 4.2 was the only small SUV with permanent 4WD 50:50 split; the nearest being Mistubishi Pinin with selectable permanent 4WD (think it had a 60:40 split)

I guess this is a little too far from the original post but nevertheless interesting ;)

[anchorman]

On a 4.2 there is a conventional transaxle but then has a transfer box which is permanently engaged to a prop shaft and a conventional rear axle. Early 4.2s had a limited slip rear diff but that was dropped when later models (with round fog lights) were offered with VSC. Normally this arrangement would not work because there is no third diff in the transfer box (like a 4.1) and the front and rear axles would bind up when negotiating turns. It very cleverly gets around this by the transfer box utilising the front differential. To summarise, this is a full time 4X4. Under normal conditions the drive is split 50:50 but if a front or rear wheel slips then the differentials will distribute the drive. It is possible for the vehicle to get stuck if one front and one rear wheel loses traction but this will be minimised on the rear axle with either a LSD or the VSC on later models.

4.3s are different animals altogether. They have a very clever drive system which is far more advanced than a viscous coupling, Torsen or Haldex arrangement. It does not require a wheel to slip to engage 4X4, it is able to vary the amount of drive steplessly and automatically all the time up to a ratio of 55:45.

[Bezzer]

4.3s are different animals altogether. They have a very clever drive system which is far more advanced than a viscous coupling, Torsen or Haldex arrangement. It does not require a wheel to slip to engage 4X4, it is able to vary the amount of drive steplessly and automatically all the time up to a ratio of 55:45.

Dunno how it does it but it is clever Came home from holiday in the bad January snow beginning of the year, neighbour hadn't dared to try and get his Beemer off the drive for 3 days and reckoned I'd got no chance when I rang to check before setting out. Drove onto the estate and up the few inclines with not one iffy moment and onto the drive, neighbours face was a picture as I had a 1500kg caravan on the back as well :)

[anchorman]

4.3s are different animals altogether. They have a very clever drive system which is far more advanced than a viscous coupling, Torsen or Haldex arrangement. It does not require a wheel to slip to engage 4X4, it is able to vary the amount of drive steplessly and automatically all the time up to a ratio of 55:45.

Dunno how it does it but it is clever Came home from holiday in the bad January snow beginning of the year, neighbour hadn't dared to try and get his Beemer off the drive for 3 days and reckoned I'd got no chance when I rang to check before setting out. Drove onto the estate and up the few inclines with not one iffy moment and onto the drive, neighbours face was a picture as I had a 1500kg caravan on the back as well :)

On your XT4 it is even more sophisticated as it integrates with the VSC. It is able to monitor the severity of a skid by comparing road speed, steering wheel angle and inertia (by using a gyroscope under the passenger seat). During this time it is able to take the power and the brakes off you and apply them as necessary, brake one wheel individually to bring the back into line, maybe engage the rear axle with that clever clutch so over-run eases the back into line, resist you turning the steering wheel (but not stop you) the wrong way as to worsten the skid and then when it has finished, hand it all back to you. It can do all this without you knowing what is going on but it will put the orange light on and sound a beeper to scold you for being a numpty. It is an astonishing bit of kit when all these systems kick up together and all of a sudden you have a much better fighting chance than most other drivers of controlling a skid. We are quick to criticise our RAVs when they play up but in this respect, when the cards are down and we make a bggr of things this vehicle is one of the best ever created for saving our butt and hauling us out of the S*1t The key to this to offering this super hero level of protection is that unassuming little clutch unit on the rear axle that can vary the drive as required - very clever and very unique.

[GS John]

I was looking for something else and found this: http://www.toyotagb-press.co.uk/protected/vehicles/releases/2009/180809toy_rav4_pack.htm which might be of interest.

[bonjo]

on the 4.2 the 4WD has a 50:50 power split. What I can't remember is how much it can vary it to, with viscous couplng, there is a limit I think up to 70% to one axle.

the 4.2 NRG & VX had limited slip diff. I am quoting this from the original brochure as mine is a GX.

Any AWD/4WD system has to allow a certain slippage for normal road use. This generally is around 15%. Once this is exceeded, in a visc-coup, the extra slippage heats up the oil therefore its viscocity and changes the power distribution a bit like clutch action. This is the way I understand the principal of it.

This basic should apply to the 4.3 system: a pre-set slippage allowed, once the sensors establish this has been exceeded,the system kicks in.

In either system, slippage comes first, then the correction.

Untill you hit the diff lock button which splits the power 50:50 with no slippage allowed. This is when you can get transmission wind up if you use the car on normal grippy road. ON the modern sissy SUV's this is disengaged automatically, on the proper 4x4's the driver has to do it manually; therefore know what is going on.

Is it true that on 4.3 the 4x4 system is disengaged (i.e FWD only) when start off from stand still on full steering lock?